1. Field of the Invention
The present invention generally relates to an apparatus and methods for wellbore completion. More particularly, the invention relates to an apparatus and methods for allowing rotational movement of downhole tools. More particularly yet, the invention provides a hydraulically activated swivel.
2. Description of the Related Art
In the drilling of oil and gas wells, a wellbore is formed using a drill bit that is urged downwardly at a lower end of a drill string. After drilling a predetermined depth, the drill string and bit are removed, and the wellbore is lined with a string of steel pipe called casing. The casing provides support to the wellbore and facilitates the isolation of certain areas of the wellbore adjacent hydrocarbon bearing formations. The casing typically extends down the wellbore from the surface of the well to a designated depth. An annular area is thus defined between the outside of the casing and the earth formation. This annular area is filled with cement to permanently set the casing in the wellbore and to facilitate the isolation of production zones and fluids at different depths within the wellbore.
It is common to employ more than one string of casing in a wellbore. In this respect, a first string of casing is set in the wellbore when the well is drilled to a first designated depth. The well is then drilled to a second designated depth, and a second string of casing, or liner, is run into the well to a depth, whereby the upper portion of the second liner is overlapping the lower portion of the first string of casing. The second liner string is then fixed or hung in the wellbore, usually by some mechanical slip mechanism well-known in the art, and cemented. This process is typically repeated with additional casing strings until the well has been drilled to total depth.
A recent trend in well completion has been the advent of expandable tubular technology. It has been discovered that both slotted and solid tubulars can be expanded in situ so as to enlarge their inner diameter. This, in turn, enlarges the path through which both fluid and downhole tools may travel. Also, expansion technology enables a smaller tubular to be run into a larger tubular, and then expanded so that a portion of the smaller tubular is in contact with the larger tubular therearound. Tubulars are expanded by the use of a cone-shaped mandrel or by an expander tool with expandable, fluid actuated members disposed on a body and run into the wellbore on a tubular string. During expansion of a tubular, the tubular walls are expanded past their elastic limit. Examples of expandable tubular devices include slotted screen, joints, packers, and liners. The use of expandable tubulars as hangers and packers allows for greater fluid bypass when running in the hole, because the conventional slip mechanism and sealing mechanism are eliminated.
Generally, a liner is a string of casing that does not extend to the top of the wellbore, but instead is anchored or suspended from inside the bottom of the previous tubular string. Multiple uses for expandable liners are being discovered. For example, an intermediate liner can be hung off of a string of surface casing by expanding an upper portion of the intermediate liner into frictional contact with the lower portion of surface casing therearound. This allows for the hanging of a string of liner without the need for a separate slip assembly as described above. Additional applications for the expansion of downhole liners exist. These include the use of an expandable sand screen, employment of an expandable seat for seating a diverter tool, and the use of an expandable seat for setting a packer.
An expandable liner is typically run into the wellbore with a running assembly disposed at an end of a drill string. Typically, a conventional swivel is connected directly to the running tool and the expander tool to interact with the running assembly during the expansion operation. The running assembly includes an expander tool and a running tool. Generally, the expander tool is disposed at the bottom end of the drill string and the running tool is located below the expander tool. The conventional swivel attaches to the running assembly between the expander and the running tool, thereby allowing the expander tool to rotate while the running tool remains stationary. Additionally, the running tool is mechanically attached to the liner through a mechanical holding device.
After the expandable liner is lowered to a predetermined point near the end of an existing casing string, the upper portion of the liner is ready to be expanded into contact with the casing. To activate the expander tool, a hydraulic isolation device, like a ball, is circulated down into a seat in the expander tool. Thereafter, fluid is pumped from the surface of the wellbore down the drill string into the expander tool. When the fluid pressure builds up to a predetermined level, the expander tool is activated, thereby starting the expansion operation. During the expansion operation, the conventional swivel on the expandable liner allows the expander tool to rotate while the liner and the running tool remain stationary.
After the liner has been expanded against the casing, the running tool is disengaged from the liner, thereby transferring the weight of the liner string to the casing. Generally, the running tool includes a primary release system that is activated by pressuring up beyond the pressure reached for expansion. Thereafter, the fluid pressure is increased to a predetermined level to deactivate the running tool, thereby releasing the running tool from the liner. The running tool typically includes a secondary or back-up release for disengaging the liner from running tool if the primary release system fails to operate properly. In the event of a hydraulic failure, the back-up release permits the running tool to release the liner by a mechanical means. Typically, the back-up release involves left-hand rotation of the running tool by the drill string. As the drill string rotates to the left, the rotational force causes a mechanism within the running tool mechanically disconnect the running tool from the liner. After the running tool is disengaged from the liner, the running assembly is removed from the wellbore while the expanded liner remains downhole.
Several problems may occur using a conventional swivel and the running assembly to expand a liner downhole. One problem particularly associated with running the liner into the wellbore is the likelihood of encountering a downhole obstruction. In this event, the liner including the expander tool, conventional swivel, and running tool may need to be rotated in one direction, thereby allowing the liner to be “drilled” into the wellbore to overcome the obstruction. However, the conventional swivel does not permit the running assembly to act as one rotationally locked unit. Another problem is associated with the removal of the running tool from the liner after the expansion operation. When the running tool primary release mechanism fails to operate properly, it may be necessary to rotate the running tool to the left to mechanically disconnect the running tool from the liner. However, the conventional swivel does not have the functionality to release the running tool by rotating the swivel in a single direction.
A need therefore exists for an apparatus for expanding a liner without swivel that allows the running assembly to selectively act as one rotationally locked unit. There is a further need for an apparatus having the capability to support the entire weight of a string of liner while providing rotational freedom between an expanding tool and running tool. There is yet a further need for an apparatus to rotate the running tool to the left to mechanically disconnect the running tool from the liner in the event of a failure of primary release system due to a hydraulic malfunction.